The present invention is concerned with a carrier matrix dissolvably impregnated with reagent and with a process for the production thereof, as well as with the use thereof.
More particularly, the present invention is concerned with the use of a special carrier matrix for dissolvable impregnation with reagents.
In clinical diagnosis, as well as also in the analysis of foodstuffs, articles of consumption and water, many frequently occurring parameters are determined. For this purpose, detection processes with the use of enzymes or detection processes with the use of immunologically active substances are often carried out. For these determinations to be carried out continually, previously produced test kits are already commercially available which contain all the components necessary for an analysis. In the simplest form, the individual components are present in the form of solutions which are mixed in appropriate amounts with the sample to be investigated. However, many substances, especially biologically active molecules, are not stable in solution and cannot be stored in this form for a comparatively long period of time. In order to avoid this disadvantage, such substances are often stored in dry form and only dissolved immediately before carrying out the analysis in an appropriate liquid and used in the form of a solution. For example, lyophilisates can be so used. However, a disadvantage of lyophilisates is the process for the preparation thereof, which is very laborious and expensive.
It is also known to press substances in solid form into tablets and thus to produce dosage units. However, problems frequently arise when these tablets are pressed too hard because they then only dissolve with difficulty. If, on the other hand, they are not pressed hard enough, the tablets have an insufficient hardness and crumble so that the dosing becomes inexact.
In order to avoid these disadvantages, it has already been suggested to impregnate paper fleece with reagents and then to introduce these paper fleece into the reaction solution during the determination process. For this purpose, the reagent must, on the one hand, adhere very well to the paper fleece in order that the amount which is impregnated on the fleece is not changed due to premature loosening. On the other hand, it is necessary that the applied reagent is eluted quickly and completely when the paper fleece is introduced into the reaction solution. The previously known paper fleece are not satisfactory in these respects since they either do not bind the applied reagent sufficiently well so that, even during storage, a part of the applied reagent is detached or the binding of the reagent is so strong that it cannot be eluted quickly and completely.
In recent years, especially for clinical diagnoses for the investigation of body fluids, for example urine, blood or samples derived from blood, such as serum or plasma, so-called carrier-bound tests have been increasingly used. In the case of these tests, dry reagents are present in or on at least one solid carrier layer which is brought into contact with the sample to be tested. Depending upon the purpose which such a test layer is to fulfill in the carrier-bound test, the reagents can be present in fixed form or in elutable form on the test layer functioning as reagent carrier.
From published European Patent Application No. 0,262,445, there is known, for example, a multi-layer test carrier for the analysis of liquids, especially of body fluids, such as blood and urine, which contains a liquid-absorbing layer which takes up the sample liquid and in which the reagents necessary for the detection reaction are present in different layers separated from one another on different carriers. In order to react the reagents with the components of the sample to be detected exclusively in the liquid-absorbing layer, it is necessary that the reagents, upon contacting the liquid to be investigated, pass completely from the test layer into the liquid-absorbing layer. As appropriate test layers, besides papers impregnated with reagents, there are suggested especially those which contain the reagents embedded in a film of water-soluble material. The film is to consist of a high molecular weight, polymeric material, xanthan being described as preferred. A disadvantage of such test layers is that, when the reagents go into solution, the film-forming material also gets into the sample to be investigated. Under certain circumstances, this can lead to disturbances, for example if the film-forming material interacts with the sample components to be determined. Especially high molecular weight, polymeric, water-soluble materials considerably increase the viscosity of the dissolving liquid, even in low concentrations. The detection reactions then often take place very slowly, being controlled by diffusion. The dissolving of the reagent from the film functioning as the carrier by means of diffusion can be considerably delayed. However, it is often desired that the reagents go into solution very quickly upon contact with a liquid so that the detection reaction takes place very quickly.